1. Field of the Invention
This invention relates to a method of and apparatus for sewing on buttons and wrapping neck thread automatically and accurately by utilizing an electronic control device, in a button sewing machine.
2. Description of the Related Art
Conventionally, a button sewing machine performs two procedures, namely, a first procedure of sewing a pattern to secure buttons on cloth with a neck thread by utilizing cams and other parts associated with each such pattern and a second procedure of wrapping a thread around the neck thread.
Prior art electric sewing machines capable of changing sewing patterns are disclosed in Japanese Patent Application Publications No. 58-58119 and No. 62-48510, for example. However, since these sewing machines adopt ROM (read-only memory) which is programmable, a large quantity of ROM is required for changing a button sewing-on pattern according to the kinds of buttons, cloths, or threads.
Although memory of a large capacity is available at the present time, it is not practical for use in a button sewing machine because too much labor is required to program the ROM with combinations of data representative of machine control commands for carrying out all of the various sewing patterns. In addition, in the case where a new sewing pattern has been created, the ROM would have to be replaced with a new one.
Further, when a button is sewn mechanically on a cloth by such conventional sewing machines using a cam device and other means, a wrapping thread is wrapped only around the outside of the neck thread and therefore such problems as the neck thread getting loose and skip stitches are likely to occur. Moreover, whenever the predetermined stitch number must be changed owing to a change in the sewing pattern, the sewing machine must be disassembled to exchange cams and other parts. This is not only troublesome and inefficient but also involves costs associated with the time and labor for disassembling and reassembling the sewing machine. Furthermore, according to the change of sewing pattern, the ROM containing machine control information for the button sewing-on pattern must be changed. This requires not only time and labor associated with such a change but also requires maintaining an inventory of ROM covering all kinds of sewing patterns. Thus, this also involves unnecessary expenses, time and labor.